This invention relates to a device for measuring the value of a resistance through which a bias current is to be passed and across which a bias voltage is to be generated.
The measurement methods used most frequently are based on the application of Ohm's law, in accordance with which the value of a resistance is equal to the quotient of the value of the voltage appearing across this resistance and the value of the current flowing through it. Therefore, it suffices to measure the bias current and voltage to derive the value of the resistance directly therefrom. Though such a method can be implemented comparatively easily for measuring the resistance of a discrete component, this method is ill-suited for measuring the resistance of a component integrated in a unit, which component may then not be accessible at all from the exterior of the unit. This is the case, for example, for the measurement of the quiescent resistance of a magnetoresistive bar integrated in a read head for reading magnetic information, during which measurement it is obviously out of the question to connect a voltmeter in parallel with the magnetoresistive bar and an ammeter in series with said bar. Moreover, if it is to be utilized, the measurement result, i.e. the value of the resistance, should be expressed in the form of an electric signal, which in many cases should take a digital form.